What is the Patriot missile defense system?

President Biden announced on Wednesday that the U.S. would provide Ukraine with the Patriot missile defense system to help defend Kyiv from an onslaught of Russian missile strikes.

At a press conference with Ukrainian President Volodymyr Zelensky, Biden called the defense system a “critical asset” for the country and “the best” in air defense.

And Zelensky on Wednesday said the “strongest element” of the latest round of U.S. aid for Ukraine was the Patriot defense system.

“This is a very important step to create a secure air space for Ukraine,” the Ukrainian leader said. “That’s the only way we would be able to deprive [Russia] and their terror attack to strike our energy structure, our people.”

The MIM-104 Patriot is the most advanced air and missile defense system in the world, used by more than a dozen countries. The Patriot is capable of engaging ballistic and cruise missiles, as well as enemy aircraft.

The Pentagon first developed the concept of the Patriot through similar predecessors in the 1960s and 1970s.

In 1976, the Defense Department revised the Surface-to-Air Missile Development and renamed it as the Phased Array Tracking Radar to Intercept On Target (PATRIOT).

The Patriot entered into full production in 1980 and saw its first combat deployment during the 1991 Gulf War.

A standard Patriot battery pack includes a radar set for tracking and detection, an engagement control station for communication, power generators, antenna mast, support vehicles and launch stations.

The launcher is equipped on a two-axle trailer toward the back of a truck, as seen in this demonstration video from the Center for Strategic and International Studies. A typical Patriot battery pack includes six to eight launchers.

The system employs two different missile interceptor types, the PAC-2 and the lighter and newer PAC-3, both of which can travel at more than 3,000 miles per hour once fired.

“A PAC-2 Patriot missile will detonate in the vicinity of the threat missile whereas a PAC-3 will seek to impact the warhead of the threat ballistic missile,” a NATO fact sheet reads.

Each Patriot launcher has four canisters, which can hold up to four missiles, depending on the type used.

The primary contract developers for Patriot systems and technology are private companies Raytheon and Lockheed Martin.